Fibrillated fabrics and a process for the preparation thereof



Nov. 24, 1970 H. l.. ElcKHoFF 3,542,632

FIBRILLATED FABRICS AND -A PROCESS FR THE PREPARATION vTIIEHEIOF Filed Feb. 2a. 1969 Fig; 1N

` //v VEN ron. H e ry Louis E ick/'off ATTORNEY United States Patent Oihce 3,542,632 FIBRILLATED FABRICS AND A PROCESS FOR THE PREPARATION THEREOF Henry Louis Eickholf, Hazelhurst, Ga., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Filed Feb. 28, 1969, Ser. No. 803,205 Int. Cl. Dc 17/02 U.S. Cl. 161-65 9 Claims ABSTRACT OF THE DISCLOSURE inter-alia, as primary and secondary backing for tuftedpile fabrics.

BACKGROUND OF THE INVENTION This invention relates generally to textile fabrics made from synthetic materials. More specifically it relates t0 fabrics woven from polyolefin ribbon yarns which have been given improved hand and properties by subjecting them to a fibrillation treatment subsequent to Weaving.

Fabrics woven of polyolefin ribbon yarn have achieved commercial success in recent years in such areas as carpet backing, industrial bagging and upholstery fabrics. The yarns from which these fabrics are woven have a generally fiat cross-sectional shape and are usually manufactured by extruding a polyolefin resin into a film of suitable thickness and then slitting the film into yarn ribbons of appropriate width. Ribbon yarn can be longitudinally oriented to possess a high tensile strength, is easy to fabricate into a Woven material, and is very economical, allowing the production of a fabric having the maximum area and strength for the amount of raw material employed.

In addition to being very economical, woven fabrics of polyolefin ribbon yarns exhibit the advantageous physical properties of polyolefin fabrics generally, including high strength to weight ratio, resistance to most solvents and many chemicals, flexibility, dimensional stability, and complete resistance to deterioration from moisture and mildew. By polyolefin materials I am referring especially to high density polyethylene and isotactic polypropylene, but other polyolefins having similar structural characteristcs are suitable for use with my invention and are included Within its scope.

Although there are many potential applications for fabrics woven of polyolefin ribbon yarns, physical properties characteristic of polyolefins create difficulties in using the fabrics in some applications. For example, the natural smoothness of polyolen ribbon yarns results in fabrics having slippery and glossy exterior surfaces. Fabrics having glossy surfaces are not desirable for applications such as industrial bagging since it is difficult to store and transport large stacks of slippery-surfaced bags. Another problem encountered in some applications is noise. The sharp edges and broad faces of the ribbon yarns produce a substantial amount of rustling and crackling when the yarns rub against each other either from motion in the weave or, more especially, when one piece of fabric comes in contact with another. Noise problems of this sort have slowed down acceptance of ribbon yarn fabrics in such applications as upholstery materials for outdoor and patio furniture.

Still another problem encountered with polyolefin ribbon yarn fabrics is their handf Hand is a term 3,542,632 Patented Nov. 24, 1970 employed in the textile industry to describe the general tacticity or feel of a fabric, and involves such factors as softness and bulk. Since polyolefin ribbon yarns are generally only a few mils thick and have a slippery surface, fabrics woven from them bear little resemblence in hand to fabrics Woven from natural fibers which have established a standard of commercial acceptability for many uses.

The smooth surface of polyolefn yarns also creates problems in use of fabrics woven from them as backing materials for tufted pile carpets and rugs. Most carpets today are made by a tufting process in which loops of pile yarns are tufted through a Woven primary backing material and then adhesively bonded to the backing by applying a layer of latex to the underside of the carpet. In higher quality carpets a secondary backing is applied over the latex to give the carpet better hand and dimensional stability. Because of the slippery, impervious surface of the polyolefin yarns, commercially available latexes do not form strong bonds with ribbon yarn backing fabrics. These problems of adhesion have not deterred the use of ribbon yarn fabrics as primary backing since the fibrous pile yarns piercing the primary back are receptive to the latex, but it has not heretofore been possible to produce a commercially acceptable secondary carpet backing woven of polyolefin ribbon yarns because of the unsatisfactory bonding between the latex and the backing fabric.

While it is possible to overcome many of the shortcomings mentioned above by using bulked or texturized synthetic yarns in the manufacture of synthetic fabrics, it has not heretofore been possible to take advantage of the ease of fabrication and economy of the ribbon yarns and at the same time produce a fabric having both the advantages of a synthetic material and much the same hand, softness, and adhesive qualities of a fabric Woven of natural fibers. I have now discovered fabrics having these desirable characteristics and methods of producing them.

SUMMARY OF THE INVENTION Brieiiy stated, my invention comprises subjecting a fabric Woven of polyolefin ribbon yarns to a fibrillating means to produce a fabric having improved physical characteristics. The fibrillation may be accomplished by the mpingement of grit particles, for example, Sandblasting, or by mechanical abrading such as contact with an abrasive wheel, or by passing the woven fabric through a zone of barbed needles such as a reciprocating needle machine.

The fibrillation may be performed as an individual operation or it may be part of a continuous operation in which polyolefin film is extruded from the resin, the film quenched and slit into ribbons, the ribbons oriented to attain high tensile strength and then woven into a fabric and the fabric heat treated to achieve dimensional stability and then fibrillated to result in better hand, adhesive qualities, quietness, and so forth. The fibrillation step in such as continuous process can precede the heat treating step, resulting in a fabric With locking between the warp and filling yarns.

My invention also contemplates tufted pile fabrics which employ the fibrillated, Woven synthetic fabrics as primary and secondary backing. These and other aspects of my invention will be more fully set out below.

DESCRIPTION OF THE DRAWINGS FIG, l is a plan view of a closely woven fabric in accordance with my invention which has been fibrillated subsequent t0 the weaving operation and then heat treated to cause locking between warp and filling yarns.

FIG. 2 is a plan view of a loosely woven fabric according'to'myinvention'which has been" severely fibrillated subsequent to the weaving operation.

FIG. 3 is a cross-sectional view of a tufted pile fabric in accordance with my invention which employs as primary and secondary backing fibrillated fabrics of this invention.

FIGS. 4a, 4b, and 4c illustrate suitable needle designs for use in the fibrillating process of this invention.

-DETAILED DESCRIPTION OF THE INVENTION Fibrillation process Fabrics woven of polyolefin ribbon yarn are subjected according to my invention, to a fibrillating means to produce a ribbon yarn fabric more similar to fabrics woven of natural fibers than those heretofore known to the art. The fibrillating means may be operated as a discontinuous operation performed in a batch manner on pre-woven fabrics from any source, or it may be part of a continuous operation for the production of finished fabrics from polyolefin resins. In a continuous operation the fibrillation step is performed subsequent to the weaving operation, but its precise placement in the process fiow depends on the particular type of fabric being manufactured. For example, a fabric with maximum fibrillated effect is prepared by locating the fibrillating means at the end of the process flow. On the other hand a fabric with minimized fibrillated effect, but `with excellent locking between the warp and filling yarns is prepared by fibrillating the prewoven fabric prior to heat treating for dimensional stabilization.

The fibrillating means may comprise any of three basic types: grit impingement, mechanical abrading or barbed needling. Since the ribbon yarns are nearly always oriented in the direction of their length, they are easily fractured in this direction into a plurality of fibers having fibrils broken out from their edges. The resulting fabric has a fuzzy look and feel much like that of a natural fiber fabric.

Grit impingement means of fibrillating contemplated by my invention include compressed air Sandblasting or pellet blasting, or suitable mechanical means of propelling a grit against the surface of the woven fabric. Methods of fibrillating by mechanical abrading include contacting the surface of the woven fabric with a rotary wire wheel, grindstone, or other abrasive source.

The preferred means of performing the fibrillation is a needling operation in which barbed needles of suitable design are caused to pierce the yarns of the woven fabric so that fibrils break out on the yarn surfaces. A preferred embodiment of the needling operation is a reciprocating needle zone such as the needling machine manufactured by the James Hunter Machine Company, North Adams, Mass., although other modes of needling such as a revolving needle roll are within the scope of my invention. The degree of fibrillation desired will determine the exact design of the needles for use in the needling operation. In general these needles should be of sufficient size and barb design to fracture the yarns in the direction of their orientation, but not so large or severely barbed that their use will result in a tearing of the fabric or a transverse breaking of the yarns. Examples or representative needles suitable for use with my process are shown in FIGS. 4a, 4b, and 4c.

Fabrics Fabrics produced according to my invention can vary from lightly fibrillated fabrics which retain Amuch of their gloss and natural feel to severely fibrillated fabrics ywhich have essentially lost the characteristic gloss and feel of the polyolefin ribbon yarns. The final product may have a fuzzy appearance and feel or it may regain a certain glossiness by a coating or heat treatment subsequent to the fibrillation. The character of the pre-fibrillated woven fabric will, of course, be very much determinative of the final product. Thus for example, a loosely woven fabric Cit having interstices between the warp and filling yarns can be fibrillated until it has a hand similar to woven jute. Material of this type is advantageous for use as a secondary backing in tufted pile carpets where a relatively fibrous surface is required to adhere the second back securely to the latexes commonly employed. As another example, I have found that when a closely woven essentially nonforaminous polyolefin ribbon yarn fabric is lightly fibrillated and then subjected to a heat treatment adequate to stabilize the fabric dimensions, a superior material for use as primary carpet backing is produced. In such a process the heat treatment tends to melt back the intertwined yarn fibrils broken out during the fibrillation and a fabric having locked warp and filling yarns is produced.

It will be apparent to one skilled in the art that the fabrics described are but two of a wide variety of fabrics which are within the scope of my invention. Such variables as the width and thickness of the polyolefin ribbon yarns, the number of ends and picks in the weave, the design of the fibrillating needles, the extent of fibrillation, and treatment subsequent to fibrillation can be variously combined to produce a full spectrum of fabrics tailored in their specifications to meet Whatever needs arise.

Pile fabrics The advantages of woven polyolefin ribbon yarn fabrics in pile fabrics as primary backings are well recognized and have been disclosed, for example, in U.S. Pats. 3,110,905 and 3,359,934. Although advantages such as economy, dimensional stability and resistance to deterioration which have made such materials successful as primary backings would suggest their use also as secondary backings, it has not until now been possible to produce a Satisfactory ribbon yarn second backing because of adhesion difficulties between the fabric and the latex. Less serious adhesion difficulties are experienced in the use of ribbon yarn fabrics as primary backings but carpets including these backings tend to ravel at newly cut edges when the carpet is trimmed during installation.

I have now discovered that these problems can be overcome by employing fabrics within the scope of my invention as primary and secondary carpet backings. FIG. 3 illustrates in cross-section a tufted pile carpet having a primary backing PB through which pile yarns 32 are tufted, a layer of latex 31 adhering the pile yarn to the primary backing, and a secondary backing SB which is applied on top of the latex and forms the actual bottom layer of the carpet. It can be seen in FIG. 3 that pile yarn protrudes through the underside of the primary backing presenting surfaces to which the latex can adhere. The secondary backing however has no such aid in adhesion and depends entirely on its own affinity for the latex to create the bond. Up to now fabrics woven of ribbon yarns have been unsuitable for secondary backing because the fabric-latex bond gives a peel test strength value of only about 3 to 5 lbs. A woven jute fabric, the most commonly used secondary backing in the industry, gives a bond strength value of about 12 to 16 lbs. The peel test is a procedure which determines the force necessary to separate the secondary backing from the latex at a uniform y rate of 12.0i0-5 inches per minute.

Referring now to FIG. 2, a fabric according to my invention is shown which is loosely woven of warp yarns 21 and filling yarns 22 so that there are interstices between the yarns and which has been severely fibrillated subsequent to dimensional stabilization giving the fabric a hand and appearance similar to burlap. This fabric, used as secondary backing SB in the pile fabric of FIG. 3, gives an average bond strength of 10 lbs. in the peel test with values ranging between 9 and l5 lbs. These values which vary with carpet design are commercially acceptable and indicate that with the novel fabrics of this invention a carpet having a polyolefin ribbon yarn second backing can be readily produced. This secondary backing is suitable for use in carpets having either synthetic or natural fiber primary backing and will, even with the use of natural liber primary backing, provide improved dimensional stability and resistance to deterioration since the actual base layer of the carpet will possess the advantages of a polyolelin fabric.

FIG. 1 illustrates a fabric according to my invention which serves as a superior primary backing for tufted fabrics. Warp yarns 11 and filling yarns 12 are closely woven so that the material is substantially non-foraminous, the fabric is lightly brillated, and the fibrillated fabric is then subjected to heat treatment for dimensional stabilization. During this heat treatment the fibrils which were formed during fibrillation on the warp and filling yarns and which are substantially intertwined due to the proximity of the yarns, melt back to the surface of the yarns effectively locking the weave of the fabric. There is a substantial locking effect simply by the fibrillation because of the intertwining of the yarn fibrils, but an especially well-locked fabric is produced by the subsequent heat treatment. While the finished material is delustered compared with the original fabric and consequently provides better adhesion with conventional latexes, the chief advantage of these materials as a primary backin-g is that a cut can be made anywhere in the backing without exposing a loose edge. This is a considerable advantage since trimming of the carpet during installation often creates loose edges Where the warp and filling yarns are not sealed together but rather are free to move relative to one another. This condition allows the carpet to ravel at the loose edges destroying the finished look of the carpet and sometimes rendering it unacceptable.

It is a preferred embodiment of my invention to employ the fibrillated and Alocked-weave primary backing described, together With the loosely Woven and severely iibrillated secondary backing according to my invention to produce a tufted pile carpet with better dimensional stability, resistance to deterioration, tuft lock and edge seal than carpets presently known to the art.

Having described my invention I claim:

1. A method for manufacturing a fabric woven of oriented polyolefin ribbon yarns which has a hand and appearance similar to that of a fabric woven of natural fiber, comprising subjecting a pre-Woven ribbon yarn fabric to a fbrillating means selected from the group consisting of grit blasting, mechanical abrading and barbed needling so that brils break-out on the surface of the ribbon yarns.

2. The -method of claim 1 in which the ribbon yarns comprise isotactic polypropylene and in which the fibrillating means comprises a zone lof reciprocating barbed needles.

3. The method of claim 1 in which the fabric is closely Woven and the fibrillating means causes the fibrils to become intertwined, and including the further step of heat treating the fabric causing the intertwined fibrils to shrink back to the surface of the yarns and lock the yarns relative to one another.

4. A fabric woven of oriented polyolefin ribbon yarns which has a hand and appearance similar to that of a natural liber fabric, manufactured by subjecting a prewoven ribbon yarn fabric to a fibrillating means selected from the group consisting of grit blasting, mechanical abrading and barbed needling so that fibrils breakout on the surface of the ribbon yarns.

5. A woven fabric of oriented polyolefin ribbon yarns having interstices between the Warp and filling yarns and having a hand and appearance similar to woven jute, manufactured by subjecting a loosely woven ribbon yarn fabric to the fibrllating action of a zone of reciprocating barbed needles so that fibrils break-out on the surface of the ribbon yarns.

6. A substantially non-foraminous fabric woven of oriented polyolefin ribbon yarns in which the warp and filling yarns are fixed relative to each other, manufactured by lightly brillating a closely woven ribbon yarn fabric by means selected from the group consisting of grit blasting, mechanical abrading and barbed needling so that fibrils break-out from the surface of the yarns and become intertwined and then heat treating the fabric causing the intertwined fibrils to shrink back to the surface of the yarns and lock the yarns relative to one another.

7. A tufted pile fabric which includes as a secondary backing the fabric of claim 5.

8. A tufted pile fabric which includes as a primary backing the fabric of claim 6.

9. The tufted pile fabric of claim 8 which additionally includes as a secondary backing the fabric of claim 5.

References Cited UNITED STATES PATENTS 3,229,346 1/ 1966 Hadley 26-28 3,283,788 11/1966 Bottomley et al. 139-28 3,359,934 12/1967 Schwertz et al. 161-65 XR 3,397,825 8/ 1968 Wilkins 28-1 XR 3,439,865 4/ 1969 Port et al 161-92 XR ROBERT F. BURNETT, Primary Examiner R. H. CRISS, Assistant Examiner U.S. Cl. X.R. 

